Crime Scene Investigation: DNA Fingerprinting

Introduction 

Over the last couple of decades, crime scene investigations have involved the subtle evolution of the DNA fingerprint techniques to the extent of the introduction and development of the polymerase chain reaction (PCR). The level of expertise brought about by PCR involved a unique extent of sensitivity in crime scenes with low-level detection of DNA. Moreover, virtually all the forensic genetic techniques used in the present-day crime scene investigations find their basis on PCR (Bashinski, 2005). 

DNA Identification and STR profiles 

DNA fingerprinting happens to be among the greatest discoveries that took place towards the end of the twentieth century. The present standards techniques that are applied in forensic DNA analysis are usually influenced by mitochondrial DNA Y chromosomes which are essentially lineage markers as well as tandem repeats (STRs). The standard genetic analysis in relation to a forensic investigation that takes place around the world often use markers of individual’s profile known as short tandem repeats (STRs). The STRs represent genetic sequences that have similarities to mini-satellites. However, the repetition of the DNA sequence exhibited by STRs is significantly shorter. There exists an equal variability among different individuals concerning STRs. The DNA Identification Act of 1994 in the United States authorized the creation of a national DNA database by the Federal Bureau of Investigation (FBI). In this regard, the national DNA database in the United States comprised of an integrated system of DNA indexes which contained different DNA profile collected crime scenes as well as forensic indexes of criminal convicts (Gruijter, Nee & Poot, 2017). 

The integrated system of DNA indexes has also been able to include forensic indexes for the arrested individuals and missing individuals. Criminal investigators can query the integrated system of DNA indexes using STR profiles obtained from crime-scene samples. It there is a match between the samples obtained from a crime scene and the profile of an individual in the integrated database, then the information obtained could most likely lead the investigator to the suspect of the crime committed or exonerate another suspect as innocent. Investigators carrying out crime-scene investigations can link different scenes of crime by performing searches about the forensic index of the samples obtained from a scene of a crime (Gruijter, Nee & Poot, 2017). 

Fingerprints Identification Types 

Three different types of fingerprints could be located by forensic investigators during a crime-scene investigation process. One of these types of fingerprints is the patent print which is easily located by naked eyes owing to its high level of visibility. The second one is the plastic print which is less common compared to the patent prints and occurs when a person’s fingers come into contact with objects like soap, butter or wax. The third type of fingerprint is the latent print whose location requires more effort due to its invisibility. The latent prints occur when a person comes into contact with surfaces that are porous or nonporous. Evidence from fingerprints associated with a victim or suspect in a scene of crime plays a critical role in guiding criminal investigators towards unraveling important detail that would lead to the arrest and conviction of the criminals involved (Bashinski, 2005). 

A better understanding of the manner in which fingerprints are located during a criminal investigation process could assist attorneys in identifying any flaws that may exist in the entire process. Moreover, a broader and deeper knowledge of the various techniques used in the location and collection of fingerprints would be useful not just for criminal investigators but also to attorneys who may be interested in cross-examining crime-scene investigators and technicians. Location of fingerprints calls for a strategic search and vigilance. However, in situations where the visibility of the fingerprints is possible using naked eyes, much effort may not be required. The type and nature of fingerprint left behind in a scene of crime usually determine the amount of effort and duration used by the investigators in locating the print (Gruijter, Nee & Poot, 2017). 

Fingerprints Recover Methods 

Alternate Light Source (ALS) 

This method of fingerprint recovery is commonly used by criminal-scene investigators to analyze and examine surfaces such as railings, doorknobs, doors, and windows using an alternate source of light. Such sources of alternate light include LED or laser devices with the ability to emit the required particular spectrum or wavelength of light. In this case, certain devices used in the emission of light contain different types of filters that are used in the provision of various spectra. These spectra are later photographed and processed further with dye stains or powders (Bashinski, 2005). 

Cyanoacrylate 

Investigators performing crime-scene investigations often carry out processing of cyanoacrylate or superglue fuming of different surfaces before the dye stains or powders. This method of recovering fingerprints is typically adopted when examining surfaces that are non-porous where the targeted objects and surfaces are exposed to cyanoacrylate fumes of vapors. In this case, the fumes of vapors are expected to stick to any fingerprints present on the object or surface thus making it possible for them to be visible using a white source of light or an oblique ambient source of light (Bashinski, 2005). 

Chemical Developers 

This method typically involves the processing of porous surfaces using chemicals such as ninhydrin. Moreover, this method involves the application of certain forms of the physical developer in revealing the latent types of fingerprints present on different surfaces or objects. The chemicals used in this particular method of fingerprint recovery usually react with certain parts of the residue from the latent print such as organic salts and amino acids. The Ninhydrin chemical changes the color of prints to purple color thus making it easy for them to be photographed (Bashinski, 2005). 

Recent Court Cases Relating to Fingerprint Identification 

One of such cases involved a situation where a senior judge questioned the fingerprint identification evidence presented before a court of law. In this respect, the judge warned that the use of fingerprint evidence in criminal trials could be marred by wrong analysis or identification thus leading to the conviction of innocent individuals. In this particular case, the appeal judge, Lord Justice Leveson raised concerns regarding the process of fingerprint identification terming it as unassailable when it comes to subjecting individuals to criminal trial proceedings. Furthermore, the judge noted that there were previous instances where innocent individuals were singled out based on erroneous analysis and presentation of fingerprint evidence (Edwards, 2018). 

In this case, the judge observed that the analysis and examination of the fingerprints by investigators was fundamentally subjective to the extent that it could be associated with inherent possibilities of misidentifications. To this extent, there is need to carry out new studies with the objective of determining the robustness and reliability of the fingerprint identification process as a way of generating evidence used to convict criminals in a court of law. Examples of cases where fingerprint identification failed to include that of Brandon Mayfield who was erroneously linked to the bombing of the Madrid train in the year 2004. The wrong analysis and identification of the fingerprint were carried out by the Federal Bureau of Investigation experts from the United States. In the year 1997, a Scottish by the name Shirley McKie was wrongly linked with a scene of a murder after a print that supposedly matched her fingerprint was discovered on the surfaces close to the body of the victim (Edwards, 2018). 

Conclusion 

In summing up, STR profiles and databases, as well as fingerprint location and identification, plays a critical role in facilitating forensic investigations in different crime-scenes. The ease of interpretation of STR profile has presently contributed towards the creation of extensive and broad databases capable of storing millions of STR profiles belonging to people who are convicted or suspected of committing crimes. 

References 

Bashinski, J. (2005). Review of: Techniques of Crime Scene Investigation, 7th edition, and Techniques of Crime Scene Investigation Interactive Training CD-ROM. Journal Of Forensic Sciences , 50 (1), 1-1. http://dx.doi.org/10.1520/jfs2004351 

Edwards, R. (2018). Fingerprint identification evidence questioned by a senior judge . Telegraph.co.uk . Retrieved 14 March 2018, from 

https://www.telegraph.co.uk/news/uknews/law-and-order/8144044/Fingerprint identification-evidence-questioned-by-senior-judge.html 

Gruijter, M., Nee, C., & Poot, C. (2017). Identification at the crime scene: The sooner, the better? The interpretation of rapid identification information by CSIs at the crime scene. Science & Justice , 57 (4), 296-306. http://dx.doi.org/10.1016/j.scijus.2017.03.006